The performance of water-soluble fluoride transformation in soil-tea-tea infusion chain system and the potential health risk assessment.

BACKGROUND: Water-soluble fluoride (WS-F) can be absorbed directly by tea plants from soil and comprises a major source of dietary F in tea consumers. To reveal the WS-F accumulation in tea leaves and assess WS-F health risks, 70 sets of samples including tea leaves at three maturity stages and corresponding topsoil were collected from Xinyang, China. The WS-F contents in tea samples and pH values in soil samples were determined. RESULTS: The contents of WS-F in tea leaves exhibited a positive correlation with leaf maturity. The contents of WS-F in tea leaves showed a positive correlation with WS-F contents in the soil as the soil pH value exceeds 5. All the bud with two leaves samples, 84.29% of the third to sixth leaves samples, and 78.57% mature leaves samples in 5-min infusion tend to be no health threat. The leaching characteristics of WS-F from tea leaves were influenced by the leaf maturity and soaking time. CONCLUSION: Taking measures to control pH and WS-F concentration of plantations soil, as well as drinking tea infusion made from young leaves or reducing soaking time could decrease the WS-F health risk. © 2021 Society of Chemical Industry.

Potential fluoride exposure from selected food crops grown in high fluoride soils in the Makueni County, south-eastern Kenya.

Makueni County, located in south-eastern Kenya, faces challenges such as limited potable water and restricted food supplies as the result of semi-aridity. High fluoride (F) concentrations have been reported in drinking water with resultant dental fluorosis affecting the local population. To determine the potential F exposure through the consumption of food crops grown in the area, F concentration was assessed in the main five locally grown and consumed crops. Additionally, the water-soluble F fraction was determined from 30 soil samples with mineralogical determination of 20 samples. Mean F concentration in the food crops was in the order; 700, 288, 71.2, 36.6, and 29 mg/kg in kale, cowpeas leaves, green grams, cowpeas (legume portion), and maize, respectively. The F concentration in farm soils ranged from 0 to 3.47 mg/kg (mean of 0.87 mg/kg) and showed a significant strong positive correlation (p = 0.03, r = 0.89) with F values in the crops. Apatite, muscovite, and biotite were identified as the F-rich minerals present. While considering two hypothetical F absorption fractions (75 and 100%), the estimated average daily dose (EADD) of F from consuming the crops ranged between 0.004 and 65.17 mg/kg/day where the highest values were from the vegetables. Most of these values were higher than the F reference dose (RfD) of 0.06 mg/kg. The estimated EADD values of several hypothetical meals prepared from the analyzed crops revealed that steamed kale and maize porridge pose the highest health risk of F associated diseases to the local population, whereas boiled cowpeas pose no health risk. Children, due to their higher daily energy requirement and low body weight, were the most vulnerable group at risk of high daily F intake relative to the RfD. These results suggest that consumption of the analyzed food crops in Makueni County may significantly contribute to F related diseases in the local population. This creates a food security issue for the area because of the potential health risks associated with these crops which are highly relied upon in the semi-arid area with a limited selection of food crops available and viable to grow.